1. Field of the Invention
This invention relates to a magnetic recording and reproducing apparatus for magnetic recording or reproduction of information on or from a magnetic tape. More particularly, the invention relates to an apparatus of the kind arranged to be loaded with a supply reel having the magnetic tape wound around it and a take-up reel; to transport the magnetic tape from the supply reel to the take-up reel by driving and rotating forward the two reels and a capstan with the tape pushed into contact with the capstan; and to rewind the tape by moving it from the take-up reel back onto the supply reel by driving them backward.
2. Description of the Related Art
The magnetic recording and reproducing apparatuses of the above-stated kind include the video tape recorder which is called a VTR for short. The VTR is arranged to use a magnetic tape cassette (hereinafter referred to as the cassette for short). The cassette contains therein a supply reel and a take-up reel with a magnetic tape spanned and wound between and around them. In recording or reproduction, a part of the magnetic tape is pulled out from the cassette and is wrapped around a drum which has magnetic heads arranged to rotate along with the periphery thereof. With the VTR loaded with the tape in this manner, recording or reproduction is performed with the tape transported from the supply reel to the take-up reel by driving and rotating a capstan while the tape is pushed into contact with the capstan.
Before or after the recording or reproducing operation, the magnetic tape is rewound by moving the tape from the take-up reel to the supply reel as necessary. This tape rewinding action is performed by driving the capstan and the supply reel to rotate backward with the VTR left in a state of being loaded with the cassette, particularly in the case of a compact 8-mm VTR or the like. The tape rewinding action of the VTR has heretofore been arranged to be performed by setting the capstan driving and rotating speed at a given constant speed. However, this has presented a problem as described below:
FIG. 1 of the accompanying drawings shows relations obtained, during the process of tape rewinding by the above-stated VTR, among a speed at which the magnetic tape is rewound by moving it from the take-up reel, the tape winding force of the supply reel, the coil diameter of the tape coiled on the supply reel and the rotating speed of the supply reel. It has been ascertained through tests that, in cases where the wrapping angle of the magnetic tape formed with the drum is large, the tape winding force required increases accordingly as the magnetic tape rewinding speed increases. The tape winding force and the tape rewinding speed must be within a range indicated by hatching in the first quadrant part of FIG. 1. In a case where the rotation torque of the supply reel is arranged to be constant, the tape winding force of the supply reel is inversely proportional to a tape coil diameter obtained on the supply reel, as indicated in the second quadrant part of FIG. 1. The tape winding force decreases as the tape coil diameter is large. Further, as shown in the third quadrant part of FIG. 1, the rotating speed of the supply reel is in inverse proportion to the tape coil diameter and in direct proportion to the tape winding force.
While there are the above-stated relations, the conventional VTR has been arranged as follows: The tape rewinding speed is set at a fixed low speed as indicated by a characteristic curve "c" in the first quadrant part of FIG. 1 according to the tape rewinding speed obtained when the tape coil diameter is large while requiring a smaller winding force as shown by the one-dot-chain line in FIG. 1, and the capstan is arranged to be rotated at a given speed corresponding to this fixed low speed.
However, the tape can be rewound at a higher speed with a larger tape winding force while the tape coil is still in a stage of a small diameter. Whereas, the conventional arrangement has necessitated an unduly long period of time in rewinding, as the rewinding speed is fixedly set at the low speed. This inconvenience has existed not only in rewinding the tape but also in fast feeding the tape at a fast speed.